The present invention relates to a cooling-water pump arrangement structure of an engine.
It is generally known that in a multi-cylinder engine which has plural cylinder bores arranged in line, an engine body (cylinder block) and a housing of a cooling-water pump are integrally formed by casting so that the engine body contains a pump chamber of the cooling-water pump in it. Japanese Patent Laid-Open Publication No. 2002-115600, for example, discloses that the pump chamber of the cooling-water pump is formed at a protruding portion which projects toward the engine side from a front wall portion of the engine body.
Meanwhile, it is also known that the cooling-water pump is formed separately from and attached to the engine body. Japanese Patent Laid-Open Publication No. 7-127520 discloses that a pump-attachment face having a cooling-water introducing port formed thereon is formed at a side wall of a front portion of the engine body, and the cooling-water pump is attached to the pump-attachment face in a lateral attaching state.
The above-described integral forming of the engine body and the pump chamber may improve reductions of the number of components or steps of manufacturing process, but since it is necessary that some protruding portion projecting toward the engine side to form the pump chamber is provided at the front wall portion of the engine body, the engine body may inevitably have a partially-projecting irregular shape. This would cause some deterioration in providing smooth and proper casting. For example, these days the engine body has been designed in an open deck structure in which its cylinder outer wall is not connected to upper ends of its cylinder bores, and made by a high-pressure casting promptly. However, if the engine body had such a partially-projecting irregular shape described above, a smooth gas removal (exhaustion) could not be achieved in a cast, so that the casting would be deteriorated.
This matter is applicable not only to a case in which the pump chamber is integrally formed at the above-described protruding portion of the engine body by casting, but to another case in which the pump-attaching face which faces toward the engine front side is formed at the protruding portion and the cooling-water pump is attached to this face from the engine front side by bolts. That is, as the amount of projection toward the engine side for forming the pump-attaching face becomes greater, the degree of irregularity of the partially-projecting irregular shape may increase, so that the casting may be deteriorated.
Meanwhile, in case the pump-attachment face is formed at the side wall of the front portion of the engine body and the cooling-water pump is attached to the pump-attachment face in the lateral attaching state, it is not necessary to provide any protruding portion projecting toward the engine side from the engine body. However, in case some device is driven by an engine crankshaft via a belt, it may be difficult to restrain the belt from producing an improper belt noise (which may be caused by a slippage between the belts and pulleys) in case of the above-described attachment in the lateral attaching state.
Thus, it is necessary to increase a positional accuracy between a pump pulley and a crank pulley in an engine longitudinal direction in order to prevent such an improper belt noise properly. Herein, increasing the positional accuracy may be easier by controlling of forming the pump-attachment face in case of the pump-attaching portion. However, in case of the attachment in the lateral attaching state, increasing the positional accuracy cannot be achieved by the controlling of forming the pump-attachment face, so that it may be necessary that the increase of the positional accuracy in the engine longitudinal direction is achieved by using a positioning pin, for example. This positioning pin, however, is inserted into a hole formed at the side wall of the engine body for fixing, so that some positional gap may be inevitably generated. Accordingly, the positional accuracy between the pump pulley and the crank pulley in the engine longitudinal direction would deteriorate, so that some improper belt noise would occur.